Stripper and pre-draw ring for wall-ironing can bodies



Jan. 28, 1969 R. J. STOLLE ETAL 3,423,985

STRIPPER AND PRE-ISRAW RING FOR WALL-IRONING CAN BODIES Filed Feb. 4, 1966 2 5 w M r 5 P. U. m 4 F mm 2 4 y iNVENTORS 00/ se y N I.

G H m AL United States Patent 3 Claims Int. Cl. B21d 22/22, 45/00, 51/10 ABSTRACT OF THE DISCLOSURE A stripper and pre-draw ring for use in a can treating apparatus for wall ironing the side walls of over-size cups, each cup having an integral end, into can bodies, said stripper being associated with an ironing punch for removing can bodies therefrom, and said pre-draw ring being disposed intermediate said ironing punch and an ironing ring to hold said over-sized cup concentric'with said ironing punch and to initially form the side wall of said over-sized cup contiguous with said ironing punch prior to wall ironing thereof when said ironing punch moves through said ironing ring and said side wall of said cup is drawn so as to form a can body having a desired length.

This invention relates to the production of can bodies having integral ends (two-piece cans), and more particularly to improvements in wall ironing, tooling and tech nique.

Metal cans have generally been made either as threepiece cans or two-piece cans. In the three-piece can, the can body is made from sheet, metal and two separate end members are provided which are then secured to the body to complete the can. More recently, however, cans have been made in the two-piece form wherein the can body and one can end are integral and a separate end is later attached to the open end of the piece having the body with one integral end.

Two-piece cans may be made in several ways. One of these is the so-called wall iron process wherein a shell cup is produced from sheet metal by conventional drawing techniques and is then redrawn to a cup of longer length and smaller diameter and the redrawn cup is then walled iron to produce the required body length and wall thickness.

A second way of forming a can body with an integral end is the so-called impact and iron forming process wherein a short cup of proper diameter but with a heavy wall thickness is formed by the so-called impactextrusion-forming process. The impact extruded short cup is then pushed through ironing dies to reduce the wall thickness and increase the length of the cup to the required length for trimming and flanging operations.

A third way of producing a can body with an integral end is the so-called impact-extrusion-forming process wherein a metal disc or slug is extruded into a die in an impact-extrusion-forming apparatus under tremendous pressure. In this process the entire forming operation is completed almost instantaneously and no further ironing of the wall is necessary.

Where a can body is formed by the so-called wall iron process, or by the so-called impact and iron forming process, a conventional cup, formed as hereinbefore indicated, is drawn to a can body of longer length by being placed on an ironing punch which is then inserted into a series of ironing rings so as to form the over-sized cup into intimate agreement with the ironing punch and to iron the cup sidewall to the proper can body length. The conventional over-sized cups are generally not con- 3,423,985 Patented Jan. 28, 1969 centric with the ironing punch because the inside diameter of the cups is appreciably greater than the diameter of the ironing punch, causing the cups to hang on the ironing punch.

While it is necessary that there be a diametric difference employed between the inside diameter of the oversized cup and the diameter of the ironing punch in order to insure easy loading of the cup onto the ironing punch, miscellaneous problems result. For example, as the diametric difference between the ironing punch and the cup increases, the amount of forming or ironing of the depending cup sides increases. However, as the diametric difference increases the possibility of the cups mis-aligning on the ironing punch at the ironing ring greatly increases. Such mis-alignment causes the ironing by the ironing ring to vary around the circumference of the cup, and often results in substantial rupture of the cup as it enters the ironing ring.

With the foregoing considerations in mind, one of the principal objects of the present invention is to provide an apparatus which will perform the basic metal forming operation of forming the sidewall of each cup into intimate contact with the ironing punchafter which time a series of ironing rings will then iron the sidewall thickness of each cup to proper can body length.

Another object of the instant invention is to provide an apparatus which will eliminate the necessity for any forming effort by the ironing rings.

It is also an object of the instant invention to provide an apparatus which will assure that the over-sized cup of material to be ironed is always concentrically located with respect to the centering of the ironing punch and the ironing rings.

Further, it is an object of the instant invention to provide an apparatus which will improve the quality of the can body which results from ironing the over-sized cup.

Another object of the instant invention is to provide an apparatus which will eliminate fracturing and rupturing of over-sized cups during the ironing process.

Still a further object of the instant invention is to provide an apparatus which will operate so that the ironing rings which iron the over-sized cups into can bodies do not perform the basic metal forming operation but only iron the sidewall thickness of each cup after the sidewall has come into intimate contact with the ironing punch.

After the over-sized cup on the ironing punch has been ironed by passing it through a series of ironing rings, the can body so formed must be removed or stripped from the ironing punch. In conventional stripping techniques, a split plate or collet type stripper is employed to bear upon the open end of the can body to physically force the can body from the ironing punch. Such a procedure has proven inadequate because it substantially damages the open end of the can body by curling, marking and splitting the end.

When the formed can body is being removed from the ironing punch a vacuum is formed in the cavity defined by the inside of the can body and the end of the ironing punch. Therefore, atmospheric pressure on the outside of the can body tends to collapse the can body as it is being removed from the ironing punch. In order to alleviate this difficulty conventional strippers employ air pressure on the inside of the ironing punch to fill the cavity so as to offset the atmospheric pressure. However, this method has also proved to be unsatisfactory.

With the foregoing considerations in mind, it is an additional object of the instant invention to provide an improved apparatus for stripping drawn or ironed can bodies from an ironing punch so as not to damage their open ends.

Finally, it is an object of the instant invention to provide an apparatus which will furnish a vacuum break so that the can bodies being removed from the ironing punch do not collapse during the actual stripping operation.

These and other objects of the invention which will be described in more detail hereinafter are accomplished by that certain construction and arrangement of parts of which the following is an exemplary embodiment.

Reference is made to the drawings forming a part hereof and in which:

FIGURE 1 is a perspective view of an over-sized cup having an integral end, as seen from the open end.

FIGURE 2 is a partial fragmentary cross-sectional view of a conventional ironing punch, having an oversized cup hanging therefrom, and an ironing ring.

FIGURE 3 is a partial fragmentary cross-sectional view of a conventional apparatus for stripping can bodies from an ironing punch.

FIGURE 4 is a perspective view of a can body having an integral end which has been ironed on a conventional ironing punch by a series of ironing rings and then removed from such ironing punch by means of a conventional stripper.

FIGURE 5 is a partial fragmentary cross-sectional view of an apparatus according to the instant invention.

Briefly, in the practice of the instant invention, and regardless of the method employed to form the over-sized cup, the over-sized cup is placed on an ironing punch and the walls thereof are ironed or drawn so that the cup is formed into a can body having an integral end. According to the instant invention the over-sized cup on the ironing punch is first subjected to a pre-draw ring before it is ironed in a series of ironing rings. As a result of the pre-drawn ring operation, the entry angle of the first ironing ring will not perform the basic metal forming operation, but will only iron the sidewall thickness of each cup after the sidewall has come into intimate contact with the ironing punch.

After the over-sized cup has proceeded through the series of ironing rings so that it is ironed into a can body having an integral end, it must then be removed from the ironing punch. Removal is accomplished according to the instant invention by means of a stripper arm, housed within the ironing punch, which moves outwardly from the end of the ironing punch, bearing uniformly upon the inside of the integral end of the can body. Simultaneously with the movement of the stripper arm outwardly, air is supplied through a valve or valves to the inside of the can body as a vacuum break so that the can body does not collapse during the stripping of the can from the ironing punch.

Referring now in more detail to the drawings, and particularly to FIGURES 1, 2, 3 and 4, conventional ironing and stripping will be explained in more detail.

FIGURE 1 shows an over-sized cup which has been produced from a sheet metal slug either by conventional drawing techniques or by the so-called impact-extrusionforming process. It should be noted that the cup 10 is relatively short and that it has a heavy sidewall thickness 12.

A conventional ironing arrangement is shown in FIG- URE 2. The over-sized cup 10 is placed upon the ironing punch 14. The diameter of the cup 10 is substantially larger than the diameter of the ironing punch 14 in order to allow for the placement of the cup 10 upon the ironing punch 14. It necessarily follows, therefore, that the cup .10 will not be concentric with respect to the ironing punch 14 because of its tendency to hang therefrom. Means (not shown) are provided for moving the ironing punch 14 through an ironing ring 16 so as to reduce the wall thickness 12 of the cup 10 and increase the length of the cup to the required length of a can body 11 before trimming and fianging operations. Due to the fact that the cup 10 is not concentric with the ironing punch 14 the side-wall ironing will vary around the circumference of the ring and, in most instances, the can body 11 so produced will not be circular, but oval, as seen in FIG- URE 4. Additionally, because substantially all the first forming is done by the ironing ring .16, where the diametric difference 18 is great, the can body so formed often ruptures, as shown at 20 in FIGURE 4.

After the wall thickness 12 of the cup 10 has been sufliciently ironed by a series of ironing rings 16 so that a proper can body 11 is formed on the ironing punch 14, the can body 11 so formed must be removed from the ironing punch 14. Removal is generally accomplished by means of a conventional stripper 22, as shown in FIGURE 3. Means are provided (not shown) for moving the stripper 22 along the sides of the ironing punch 14 to push the can body 11 off of the ironing punch 14. As can be seen, conventional strippers 22 have proven to be unsatisfactory because they damage the open end of the can body 10 by curling, marking and splitting the end, as shown at 24 in FIGURES 3 and 4.

Additionally, when the can body 10 is removed from the ironing punch a vacuum is set up in cavity 26, formed by the inside of the can body 11, the integral can end, and the end of the ironing punch 14. Atmospheric pressure acting on the outside of the can body 11 is sufiicient to buckle the can body 11 inwardly, as shown at 27 in FIGURE 3.

FIGURE 5 is a fragmentary cross-sectional view of an apparatus according to the instant invention. As can be seen, the side-wall of an over-sized cup .10 is first formed into intimate contact 29 with the ironing punch 14, and is then ironed to form the can body 11. In operation, a cup 10 is placed upon the ironing punch 14. The ironing punch is then moved through the pre-draw ring 28 and then into a series of ironing rings 16. For purpose of simplicity only two ironing rings '16 are shown. The pre-draw ring 28 performs the basic forming operation whereby the cup 10 comes into intimate contact 29 with the surface of the ironing punch 14. It should be noted that the pre-draw ring 28 assures that the cup 10 will be concentric with respect to the ironing punch 14 so that the diametric difference 18 will be substantially the same on both sides of the ironing punch. This, of course, assures that any future ironing will be uniform around the cup 10 and that the cup 10 will not rupture. The pre-d.raw ring 28 has an aperture 30 which receives the cup 10 on the ironing punch 14. The aperture 30 has rounded corners 32 which aid in aligning the cup 10.

After the cup 10 has passed through the pre-draw ring 28, the ironing punch is pushed through a series of annular ironing rings 16. Each ironing ring 16 contains an aperture 34, having a centrally located edge 35, the diameter of which is just slightly less than the diameter of the cup 10 on the ironing punch 14 after it has passed through the immediately preceding ironing ring 16 or the pre-draw ring 28, as the case may be. Each ironing ring 16 also has an angular edge 36 leading to the centrally located edge of the aperture 34. Because the pre-draw ring 28 has satisfactorily formed the side-walls of cup 10 so that they are contiguous 29 with the ironing punch 14, the ironing rings 16 simply iron the sidewall thickness of the cup 10, making it less and less, until a can body 11 of sufficient length has been formed.

It should be noted that the can body 11 formed by the ironing rings is substantially circular in shape and that the ironed side-wall does not vary around the circumference of the can body 11. Also, the can body 11 has not been ruptured. Additionally, there is much less effort required for the ironing rings 16 to properly iron the sidewalls of the cup 10.

After the side-walls of the cup 10 on the ironing punch 14 have been sufficiently ironed to form can body 11, the integral can end 38 may be domed as shown in FIGURE 5. This may be accomplished by moving the integral end 38 of the can body 11 on the ironing punch 14 against a die (not ShOWn), the diameter of which is slightly less than the diameter of the can body. The end of the ironing punch 14 is recessed to receive the die.

After the can body 11 on the ironing punch 14 has been domed as at 40, it is ready to be removed. Removal is accomplished by means of the stripper, shown generally at 42. The ironing punch 14 has a substantially concentric bore 44, somewhat enlarged at one end, extending its entire length into which a bushing 46 has been fit. An arm 48 is located Within the bushing 46. An enlarged head 50, with a circular recess to receive the domed integral can end 40, is mounted at the end of arm 48. It should be noted that the enlarged head 50 is within the ironing punch '14 when the arm 48 is retracted within the ironing punch 14.

Radial duct 52 leads into two annular chambers 54 formed by punch cap 55 which is held in place over the bushing 46 in the enlarged end of the bore 44 by cap screws 57 (only one is shown). It should be noted that the edges 56 of one annular chamber 54 act as a valve seat against which the enlarged head 50 may rest.

In operation, means are provided to move the arm 48 in an outward direction away from the ironing punch 14. Air pressure at approximately pounds per square inch is supplied to the duct 52. Immediately upon movement of the arm 48, the enlarged head 50 leaves the valve seat 56. The air pressure supplied through duct 52 immediately enters the vacuum in the cavity 58 formed by the can body and integral end as it leaves the ironing punch. For example, the movement of the stripper 42 and can body 11 in FIGURE 5 are indicated by dashed lines. Immediately when the enlarged head 50 leaves the valve seat 56, air pressure at 10 pounds per square inch enters cavity '58 to act as a vacuum break and to preclude the can bodys collapse due to atmospheric pressure acting on its sidewall.

It should be noted that the enlarged head '50 of stripper 42 has a uniform bearing against the inside of the integral can end 40. This, of course, prevents damage to the can end. Additionally, there is no damage to the can body 11 or curling or bending of the can body edge 24.

It will be understood that modifications may be made without departing from the spirit of the invention and therefore no limitations other than those specifically set forth in the claims are intended or should be implied.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a can treating apparatus for wall ironing the side walls of over-sized cups, each cup having an integral end, into can bodies of the type having a cylindrical ironing punch for receiving said over-sized cups, the outside diameter of said ironing punch being less than the inside diameter of said over-sized cups, and said ironing punch having a substantially concentric bore therein, said bore being enlarged at the cup receiving end of said ironing punch, a stripper located within said bore of said ironing punch to strip said can bodies from said ironing punch, at least one ironing ring associated with said ironing punch to iron the side walls of said over-sized cups, means for moving said ironing punch through said ironing ring, and means for actuating said stripper, the improvement which comprises at least one pre-draw ring disposed intermediate said ironing punch and said ironing ring through which said ironing punch moves prior to movement through said ironing ring, said pre-draw ring having an inside diameter which is slightly less than the outside diameter of said over-sized cup, and having the edge of said inside diameter which is first contiguous with said side wall of said over-sized cup gradually curved inwardly, whereby as said ironing punch moves through said pre-draw ring, said over-sized cup is held concentric with said ironing punch and said side wall of said oversized cup is initially formed contiguous with said ironing punch prior to wall ironing thereof when said ironing punch moves through said ironing ring and said sidewall of said cup is drawn so as to form a can body having a desired length, and wherein a portion of said stripper acts also as a gas valve to introduce gas under pressure to the inside of said can body to prevent collapse thereof during stripping.

2. The apparatus according to claim 1 wherein said stripper comprises:

(a) a reciprocable arm slidably mounted in said bore;

(b) a valve seat, said valve seat being within said enlarged portion of said bore within said ironing punch;

(c) an enlarged head defining a portion of said stripper, said head being substantially the size of said integral end of said can body and slidably mounted at the end of said arm so as to be within said'enlarged portion of said bore within said ironing punch and resting against said valve seat when said arm remains retracted within said ironing punch;

(d) means associated with said stripper to supply gas under pressure to said valve seat;

whereby as said stripper is actuated, causing said arm to reciprocate in said bore, said head is caused to bear uniformly against the inside of the integral end of said can body to strip said can body from said ironing punch and said gas under pressure is released from said valve seat when said head is removed therefrom, said gas under pressure substantially filling the cavity formed by said side wall and said integral end of said can body and said ironing punch as said can body is stripped off said ironing punch.

3. A stripper to strip can bodies, the sidewalls of which have been wall ironed, from an ironing punch, the ironing punch having a substantially concentric bore therein which extends the length of the ironing punch and which is enlarged at the cup receiving end of the ironing punch, which comprises:

(a) a reciprocal arm slidably mounted in said bore;

(b) a valve seat, said valve seat being within said enlarged portion of said bore within said ironing punch;

(c) an enlarged head substantially the size of said integral end of said can body, said head being slidably mounted at the end of said arm so as to be within said enlarged portion of said bore within said ironing punch and resting against said valve seat when said arm remains retracted within said ironing punch, whereby said head acts as a valve against said valve seat;

(d) means associated with said stripper to supply gas under pressure to said valve seats;

whereby when said arrn reciprocates in said bore, said head is caused to bear uniformly against the inside of the integral end of said can body to strip said can body from said ironing punch and said gas under pressure is released from said valve seat when said head is removed therefrom, said gas under pressure substantially filling the cavity formed by said sidewall and said integral end of said can body and said ironing punch as said can body is being stripped off said ironing punch to prevent the collapse of said can body.

References Cited UNITED STATES PATENTS 2,379,450 7/1945 Musser 72344 3,270,544 9/1966 Maeder et al 72-346 398,229 2/ 1889 Chambers 72--345 2,261,060 10/1941 Giesler l13120 CHARLES W. LANHAM, Primary Examiner. R. D. GREFE, Assistant Examiner.

7 U8. Cl. X.R. 

